5% of bladder cancer cases in Europe, one in 20, would be linked to chemicals present in tap water, for a total of 6,561 cases per year in 26 countries on the continent. This is estimated by a study published in Environmental Health Perspectives, which shows that maximum concentrations of contaminants have exceeded the limit of 100 micrograms per liter in 9 countries, including Italy. Previous research has found an association between bladder cancer and long-term exposure to a group of chemicals called trihalomethanes (THM), such as chloroform, which have been found to be carcinogenic in animal studies and form as an unwanted by-product when the water is disinfected in the plants. To estimate the extent of the problem, researchers from the Barcelona Institute for Global Health analyzed the presence of chemicals in drinking water in the EU states between 2005 and 2018, sending questionnaires to the bodies responsible for national water quality.
Data were obtained for 26 countries, Bulgaria and Romania are missing. The estimated annual average of the levels of trihalomethanes was 11.7 micrograms per liter, or countries with the lowest averages were found to be Denmark and the Netherlands (0.2 micrograms), the highest average values were instead observed in Cyprus (66.2 micrograms) and Malta (49.4).
If instead of the averages the maximum peaks are considered, in 9 countries trilane levels exceeding 100 micrograms per liter (EU limit value) have been detected: that is Great Britain, Spain, Cyprus, Estonia, Hungary, Ireland, Italy, Poland and Portugal. The researchers estimated the number of bladder cancer cases attributable using incidence rates and trilometane levels. Analysis suggested that Cyprus had the highest percentage, with a quarter of the chemical-related diagnoses. Spain and the United Kingdom, however, have the largest absolute number of potentially related cases, 1,482 and 1,356 respectively. In the case of Italy, the connection concerns 336 cases per year. "Over the past 20 years, great efforts have been made to reduce the levels of trihalomethanes in several countries of the European Union," says co-author Manolis Kogevinas. "However, current levels in some countries may still pose a significant burden on bladder cancer, which could be avoided by optimizing water treatment." If no country exceeds the current EU average, 2,868 cases of bladder cancer per year could potentially be avoided.